Less than halfway through training camp, the Cardinals' defense is already frustrating Carson Palmer's offense.

The offense has become the underdog of the practice field, frequently frustrated by a veteran cast of defensive linemen who, nine days into practice, have learned Palmer's play calls and developed what coach Bruce Arians called "a great swagger."

"The personnel is very well built, there's good players and there's good backups, there's leadership, there's all those things you look at," Palmer said. "But more than anything, it's the scheme. Coach Bowles puts in a new defense every day, a new blitz every day, you can't get a bead on what you think is coming. He'll show you a look where they're bringing a ... free safety one day and they'll have the exact same look four periods later in practice and it's a blitz from the other side of the field that looks exactly the same."

Campbell, with more measured confidence than swagger, said he expects this year's defense to be better than last year's, which ended the season ranked the best rushing defense and seventh-best overall team defense in the league.

The defensive end also said he expects Bowles to install rotations of players in order to take full advantage of the available talent.

"It's fun, this defense does have a lot of guys who have had some success in the league, so it's kind of cool because you have confidence in the guys, with Coach Bowles drawing up the schemes that he draws up," Campbell said. "And the players, everybody's so talented, so many guys who make plays, it's just going to be fun taking turns making big plays and changing the game."

Arizona Cardinals running back Robert Hughes, left, pulls in a pass as linebacker Keenan Clayton pursues during practice at University of Phoenix Stadium in Glendale, Wednesday, August 6, 2014. Tom Tingle/azcentral sports

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Aside from his veteran teammates, Campbell made note that rookie safety Deone Bucannon caught his attention as a player who was able to quickly adapt in camp.

Arians, who praised Bucannon as a standout at the beginning of camp, said he was impressed with the safety's improvement after a quiet spring. Both Arians and Campbell agree it was a mental hump — perhaps the pressure of living up to his 27th overall draft selection — Bucannon had to get over.

"Most rookies when they come in they're a little nervous and they don't know what to expect," Campbnell said. "So you just have to kind of put your arm around them and teach them all the small things. Some guys get it, like Bucannon, he has a pretty good mind-set and you can tell his eyes just opened up pretty quick, so he gets it right away."

Arians said what he has seen of the defense's depth in training camp makes it that much harder to cut players.

"It's going to be more than just the D-line, we're going to cut some really good players this year," Arians said. "And that's a testament to (General Manager Steve Keim) and (Vice President Terry McDonough) and the guys that build the roster. More so the defensive line, with some of the young kids battling it out and really coming on, it makes sense to see them when the lights come on. It's a very nice problem to have.

Injury update

Only Lyle Sendlein sat out Wednesday's practice; G Jonathan Cooper and T Nate Potter were back on field after taking Tuesday off, both with a sore knee. Dockett took a rest day at Arians' request.

Arians said Wednesday might be the first day of training camp that everyone without a serious injury was available to play, an encouraging thought with Saturday's game against the Houston Texans looming.

Kicker competition

Arians said nerves will be the deciding factor in the competition for starting kicker.

Despite incumbent Jay Feely posting solid numbers for the Cardinals over the past three years and the free-agent challenger from Clemson, Chandler Catanzaro, not making much noise in practice, Arians implied the two kickers are on equal footing.

"They're different games but they've both had big, big kicks," Arians said. "And NFL and ACC, yeah they're different, but for a kicker — my son was a kicker, so I kind of know the way that whole scenario goes, he was just as good as a rookie as he was when he got injured — but you either have nerves or you don't. That's all about nerves, because talent is not the issue with either one."

Each kicker will alternate playing full games throughout preseason, and Arians said he would evaluate after that. Catanzaro will kick Saturday against the Texans.

Fells' mindset the same

Even though starting tight end Jake Ballard announced his retirement Wednesday morning, and Arians on Monday complimented tight end Darren Fells' development, Fells said his mindset looking ahead remains unchanged.

"Anything could happen," Fells said, "someone else could come in and take my spot, so I can just keep doing what I've been doing and hopefully get to be on that roster ... ."

Arizona newcomer John Carlson is listed as the second starting tight end on the Cardinals' depth chart, released Monday. Troy Niklas and Rob Housler are slated as backups.

Before Ballard announced his retirement, Arians said he has versatile tight ends that offer him flexibility in the position, but wants to focus on improving the blocking unit.

Fells said fine-tuning his blocking has also been his first priority throughout camp.